Silverlight Application Hosting Requirements

I want to build a silverlight web application that could installed o开发者_如何学JAVAn a user's computer. So any hosting requirements would be subject to whatever configuration the user has. What are there requirements to host a silverlight application?

I need the same question answered for Flash and WPF.

1. Can any OS be used?
2. Is it required that the .Net framework (or whatever Flash uses in that case) be installed on the machine?
3. Obviously some webserver must be installed, what are the restrictions on the webserver for these three technologies?
4. Anything else?

On Silverlight:

1. Not sure if Mac has out of browser support; Linux support (Moonlight?) is a ways off I think.

2. No. Silverlight comes with its own minimal version of the CLR runtime so nothing else is needed. Flash also uses nothing else.

3. No webserver needs to be installed on the client machine; the application can communicate to the same webserver as when it's hosted in the browser.

4. Not really, but there are a bunch of helpful features in Silverlight 4 pertaining to out-of-browser applications: see here for details

I haven't developed in Flash in a long time, however I have heard of Adobe Air and it looked promising at one time, but now I'm entirely devoted to Silverlight.